WO2002080329A1

WO2002080329A1 - A compact circuit interuption device

Info

Publication number: WO2002080329A1
Application number: PCT/NZ2002/000050
Authority: WO
Inventors: Alan David Scottorn; Martin Alan Scottorn
Original assignee: Pdl Holdings Limited
Priority date: 2001-03-30
Filing date: 2002-03-28
Publication date: 2002-10-10
Also published as: WO2002080328A8; WO2002080328A1; AU2002248108A1

Abstract

In a compact circuit interruption device (10) for mounting on a distribution board, within the interior of the housing of the device a circuit board is mounted with the plane of the circuit board (45) substantially aligned with the main plane of the housing, a trip device (47), a latch (49) and a contact set (30, 32) are housed with the latch disposed within the housing with its length substantially aligned with th emain plane of the housing, and one of the contact set is supported by a moveable contact carrier (35) disposed with its length substantially aligned with main plane of the housing and a reset mechanism (51) is arranged in relation to the housing with it's length substantially aligned with the main plane of the housing.

Description

A COMPACT CIRCUIT INTERUPTION DEVICE

FIELD OF THE INTENTION

The present invention relates to circuit interruption devices which are arranged to open an electrical circuit in the event that a fault condition is detected. In particular, the invention relates to a residual current device mountable in an electrical distribution board.

BACKGROUND TO THE INVENTION

Typically, there is a limited amount of space on an electrical distribution board. Further, there are industry standards as to the maximum height, width and depth of units mounted to a distribution board. This is necessarily so because if one unit is removed, the replacement will need to fit in the remaining space. Furthermore, the front of such units usually has a user operable actuator eg a switch. Typically, such actuators are accessible through an aperture provided in a barrier fitted onto the distribution board. The barrier protects users from accidental contact with live parts. Therefore, there are also constraints as to the placement of actuators within such units so that they may be visible through the front window. Additionally, by convention, the terminals are usually disposed at opposite ends. These are generally quite bulky and this places further limitation on the usable space within the component. To meet international industry standards the width of each component is generally limited to 18 mm. Where the unit is to a 2-pole circuit interrupter this width limitation presents difficulties in that the space for each power cable to terminate at the terminals generally takes up the best part of this 18 mm.

SUMMARY OF THE INVENTION

It is an object of the invention to provide a circuit interruption device to fit into a confined space on a distribution board. It is an object of at least a preferred embodiment of the present invention to provide a 2-pole residual current device to fit within a space on a distribution board which would normally be occupied by a single-pole device.

In broad terms the invention comprises a circuit interruption device for mounting to a distribution rail or on a distribution board including: a housing having length, depth and thickness with the thickness dimension being the smallest, and the length and depth defining a main plane of the housing; a circuit board of planar configuration mounted within the housing so that the plane of the circuit board is substantially aligned with the main plane of the housing, the circuit board providing a mounting for at least some components of a fault detection circuit to detect a fault condition; a trip device, a latch and a contact set, which trip device will in response to detection of a fault condition trigger the latch to open the contact set, the latch having length, breadth and thickness and being disposed within the housing with its length substantially aligned with the main plane of the housing, and one of the contact set being supported by a moveable contact carrier having length and being disposed within the housing with its length substantially aligned with the main plane of the housing; and, a reset mechanism to reset the contact carrier to close the contact pair, the mechanism including an actuator having length, and which is arranged in relation to the housing with it's length substantially aligned with the main plane of the housing.

There could also be two contact sets as in a 2-pole device with one of each set supported on the moveable contact carrier and the other of each set being a fixed contact.

Preferably, the housing includes end portions at each end for terminal connections. There will be two terminals at each end and preferably, these terminals are both substantially aligned in the main plane. Preferably, each terminal has an associated terminal port, resulting in two terminal ports at each end and preferably the two terminal ports are arranged one atop the other.

Suitably, the housing includes a central portion defining a main cavity for the circuit board, the trip device, the latch, the contact sets and the contact carrier and at least a portion of the reset mechanism and the actuator, forming part of the reset mechanism is disposed at the front of the central portion of the housing and, protrudes through a front wall of the central portion of the housing.

The fault detection circuit preferably includes a sensor coil, through which active and neutral conductors pass and wherein the axis of the coil is arranged to lie substantially aligned with the main plane of the housing enabling the conductors to pass through the sensor coil generally aligned with the main plane of the housing. In order to achieve this, in a preferred form of the invention, the sensor coil straddles the circuit board and the two conductors pass on either side of the circuit board. In a most preferred form of the invention, the circuit board is centrally disposed relative to the thickness of the housing.

The trip device may be a piezoelectric trip device or alternatively an electromechanical trip device such as a solenoid. In a preferred form of the invention, the trip device is a solenoid with an elongate body incorporating a solenoid coil with a moveable plunger operable to trigger the latch. In the present invention, it is preferred that the length of the body is arranged to be aligned within the main plane of the housing. In a most preferred form of the invention, the energisible coil is wound such that its resultant transverse shape has a first transverse dimension less than a second transverse dimension orthogonal to the first transverse dimension. For example, the coil is wound over a bobbin having a transverse shape with a width dimension less than a breadth dimension. In this manner, the resultant wound configuration could be rectangular with rounded corners. Oval and elliptical cross-sectional shapes are also possible. Suitably, the cross-section is uniform over the length of the coil. In the present invention, it is preferred that the thickness dimension of the coil is arranged to be generally aligned with the thickness dimension of the housing. This will reduce space in the confined width dimension of the housing.

The latch may be of any configuration but in a preferred form of the invention the latch is L-shaped having one arm which is engaged by the trip device on tripping and another arm which engage the contact carrier to hold the contact carrier in a position whereby the contact set is closed. Preferably, the thickness of the latch is aligned with the thickness dimension of the housing. The latch pivots about a main pivot, the axis of which is aligned with the thickness dimension of the housing. In a most preferred form of the invention the latch and the trip device are disposed on opposite sides of the circuit board.

The contact carrier will suitably move from a latched position in which the contact set(s) are closed and an unlatched position in which the contact set(s) are open. The contact carrier may pivot within the main plane of the housing.

At each end, preferably two terminal connectors are arranged one slightly about the other. Each has preferably an associated terminal port, one disposed above the other in the end wall. Additionally, the barrier portion is operable to effect engagement between an auxiliary contact set. For example, an auxiliary contact set is provided such that in the event of the circuit interrupter being wired incorrectly, the movement of the moveable contact carrier to break the primary contact sets will effect breaking of the auxiliary contact set. Preferably the auxiliary contact set comprises a fixed contact and a moveable contact. In a most preferred form this moveable contact is mounted on a spring loaded contact carrier. In a preferred embodiment of the invention, the moveable contact is a spring bar and the fixed contact is defined on an edge of the circuit board.

BRIEF DESCRIPTION OF THE DRAWINGS

In order that the invention may be more fully understood, a preferred embodiment is described by way of example with reference to the drawings in which:

Figure 1 is a cut-away view of a residual current device unit in accordance with a preferred embodiment of the present invention, the device shown in the unlatched position;

Figure 2 is a side view of the RCD shown in Figure 1, in the unlatched position;

Figure 3 is the opposite side view to Figure 2;

Figure 4 is a side view as in Figure 2 except illustrating the RCD in the latched position with the contacts closed;

Figure 4a is a opposite side view to Figure 4;

Figure 5 is a side view of the RCD shown when tripping;

Figure 5 a is a side view of the interior of the housing of the RCD illustrated in Figures 1 to 5; Figure 6 is a perspective view of a contact carrier sub-assembly in the unlatched position corresponding to Figures 1 and 2;

Figure 7 is a perspective view of the contact carrier sub-assembly illustrated in the latch position corresponding to Figure 4;

Figure 8 is a perspective view of a bobbin for a solenoid used in the RCD illustrated in Figures 1 to 5, the bobbin illustrated without the solenoid coil;

Figure 9 is a transverse cross-sectional view of the bobbin illustrated in Figure 8;

Figure 10 illustrates the bobbin of Figure 8 wound with the solenoid coil;

Figures 11 and 12 are plan and end views respectively of a solenoid plunger cooperable with the solenoid bobbin illustrated in Figures 9 and 10; Figure 13 is a longitudinal cross-sectional view of the solenoid of Figure 10; Figure 14 is a circuit diagram of a fault detection circuit incorporated into the RCD illustrated in Figures 1 to 5;

Figure 15 is a perspective view of the exterior of the RCD shown in Figures 1-5; and Figure 16 is a perspective view of the RCD of Figure 15 mounted on a rail of a distribution board.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENT OF THE INVENTION

Arrangement of Main Components Within Housing Figures 1 through 5 illustrate the main components of a residual current device unit 10 appropriate for mounting in a distribution board. The unit 10 includes a housing 12 having a front region 14 and a rear base 16 to mount the housing 12 on the distribution rail 13 of a distribution board 15. (See also Figures 15 and 16). Accordingly, the rear base 16 may be appropriately shaped to fit an industry standard distribution rail 13. The housing 12 is designed to be able to fit into the existing space normally occupied by devices on the distribution rail such as miniature circuit breakers and isolation switches. Set by international industry standards, this space is about 18 mm and thus the width ie the smallest overall dimension of the housing is limited to 18 mm. Furthermore, the overall length of the housing is also limited because there is a limited amount of room on the distribution board 15 as can be appreciated from Figure 16. Reverting back to Figure 1, the terminal connections are made at either end by way of terminal connectors 20 and it can be seen from Figure 1 that a considerable amount of space is required at the end portions 24 of the assembly 10 to house the terminal connectors 20. End portions 24 are defined at each end of the housing 12. The RCD is a 2-pole device and thus each end portion 24 houses two terminal connectors 20, one for active and one for neutral respectively. The terminal connectors 20 are typical of those found in the art and will thus not be described in detail. Each terminal connector 20 has an associated terminal port 26. At each end, one port 26 is located above the other in the end wall of the housing 12. At each end, the terminal connectors are thus arranged in line but vertically offset from each other (See also Figure 15). The active and neutral lines (not shown) are connected to the terminal connectors 20 on the right hand side of Figure 1. Each of the terminal connectors 20 are connected by means of metallic connectors to respective fixed contacts 30. Moveable contacts 32 (only one of which can be seen from Figure 1) are provided on a moveable contact carrier 35 which will be described in much greater detail below. The moveable contact carrier 35 is moveable between an unlatched position illustrated in Figures 1 through 3 to a latched position illustrated in Figure 4. Each of the moveable contacts 32 are connected to respective leads 39 which pass through a sensor coil 42 to respective ones of the terminal connector 20 on the left hand side of Figure 1. The terminal connectors 20 on the left hand side are connected to the load (not shown).

The remainder of the components of the residual current device are housed within a central portion of the housing 12 between the two end portions 24. The main components include circuit board 45, sensor coil 42, trip device in the form of a solenoid 47, a latch 49 (see Figure 3), the moveable contact carrier 35 and a reset mechanism including actuator 51 (only part of the actuator resides in the housing). The actuator 51 is connected to the contact carrier 35 by a link mechanism described in greater detail in connection with Figures 6 and 7. The solenoid 47 is described in greater detail in connection with Figures 8 to 13.

The central portion of the housing 12 presents a protruding front region 14. Distribution boards 15 on which the device 10 is mounted typically have a barrier (not shown) to protect the user from contact with live components. The barrier has an aperture to allow restricted access to actuators and the like. The front portion 14 is thereby disposed such that when it is mounted to the distribution rail 13 of a distribution board 15, the front portion 14 will be accessible through the aperture in the barrier.

The circuit board 45 provides a mounting for at least most of the components of a fault detection circuit illustrated in Figure 14. Those components mounted on the circuit board 45 are depicted in Figure 14 within the rectangle drawn in phantom.

The dimension between the front portion 14 and the rear base 16 is the depth of the housing 12, with the length and depth defining a main plane of the housing as will be appreciated. The thickness dimension extends transversely to this main plane.

The circuit board 45 is planar in form and is generally aligned with the main plane of the housing 12. The circuit board 45 is disposed approximately centrally relative to the width of the housing. It can be seen from Figure 1 that the sensor coil 42 has a central hollow core through which the leads 39 pass. The sensor coil 42 is arranged so that the axis of the central core is substantially aligned with the main plane of the housing and in fact extends in the length direction of the housing. The sensor coil 42 has upper and lower mounting portions 53 to secure the sensor coil 42 within an appropriately shaped cut-out in the circuit board 45. The circuit board 45 is thus arranged to bi-sect the hollow core of the sensor coil 42 enabling each of the leads to pass on opposite sides of the circuit board 45. The trip device in the form of solenoid 47 is also mounted to an extension 55 of the circuit board extending between the solenoid 47 and the latch 49 (see Figure 3). This provides appropriate electrical connection to the solenoid 47.

The solenoid 47 has a coil which is wound on a bobbin of approximately rectangular cross-section. The solenoid 47 is thus elongate in configuration with a thickness dimension which is considerably less than its breath dimension. Accordingly, the solenoid 47 is arranged with its length and breath dimension generally aligned with the main plane of the housing and its thickness dimension generally aligned with the thickness dimension of the housing.

Detailed Description of Solenoid 47

Figure 8 illustrates a bobbin 200 for the solenoid 47 illustrated in Figures 1 to 5. The bobbin 200 is comprised of a first end portion 202 and a second end portion 204 with a central portion 206 extending therebetween. The central portion 206 is of tubular configuration having an interior periphery 208 which is rectangular in cross-section. The exterior periphery 210 of the central portion 206 is oblong in cross-section. More specifically, the transverse cross-section is rectangular in form with rounded corners and convexly rounded sides. The central portion 206 provides a spool about which the solenoid coil can be wound as illustrated in Figure 10. The resulting shape of the coil accordingly corresponds to the shape of the external periphery 210 of the central portion 206. As illustrated in Figure 10, the ends of the coil 212, 214 are wound about the exposed ends of respective pins 215, 217 extending from the top surface of the second end portion 204. The pins 215, 217 extend through the second end portion 204 to project from the base of the end portion 204 for insertion into the printed circuit board 45. The mounting onto the extension 55 of the circuit board can be seen in Figure 3. The electrical connection to the solenoid is made thereby.

The first end portion 202 of the bobbin 200 is planar in configuration with a central rectangular aperture 220. The aperture 220 is commensurate in its disposition and size with the internal periphery 208 of the central portion 206. The first end portion 202 is supported by a pair of feet portions 224, 226. Figures 11 and 12 illustrate the form of a plunger 230. The plunger 230 is of T-shaped configuration having an elongate portion 232 and a head portion 234. As can be viewed in Figure 12 the plunger 230 is of uniform thickness. The plunger 230 is constructed by being punched from metal sheet, but is not limited to being manufactured by this method. The elongate portion 232 is slidably received within the tubular central portion 206 with a sliding fit provided with the internal periphery 208 of the central portion 206. The plunger 230 extends out through the rectangular aperture 220 in the first end portion 202. It will be appreciated that the provision of a plunger having thickness dimension less than its breadth dimension slidably received within a bobbin having an internal periphery of complementary dimensions and an external periphery of reduced thickness to breadth dimension results in an overall bobbin size which is of reduced thickness compared to a conventional circular bobbin of the same power. Some space savings can be achieved in an RCD when such a solenoid is incorporated therein.

As illustrated in Figure 13, the solenoid 6 incorporates a metal plate 240 having a U- shaped configuration. The metal plate 240 has first and second end portions 242, 244 with a central portion extending therebetween. The second end portion 244 extends into the centre of the second end portion 204 of the bobbin 200, providing an abutment for the end of the plunger 7. The central portion of the U-shaped plate 240 extends underneath the bobbin 200 towards the head of the plunger 7, between feet portions 224 and 226 and upwardly along the outer end of the first portion 202 of the bobbin 200. The first portion 242 of the metal plate 240 thus extends between the spring 6a and the outer end of the first portion 202. As shown in Figure 13, the first end portion 242 of the metal plate has an aperture therethrough aligned with the aperture 220 enabling the plunger 7 to extend therethrough.

In Figure 1, it can be seen that the solenoid 6 is surrounded by a frame 57 joined to the head of the plunger 7. The frame 57 thus moves with the plunger 7. The frame 57 incorporates a contact arm 59 which extends in the thickness dimension of the housing 12 as can be seen in Figure 1 and Figure 3. In the de-energised state of the solenoid, the plunger 7 is away from the body of the solenoid 6. On energising the solenoid 6, the plunger moves towards the body. The frame transmits the movement to trip the latch arm 47. As will be explained subsequently, this tripping leads to opening of the contacts. Latch 49

The latch 49 is best viewed from Figure 3. The latch 49 generally conforms to an L- shaped configuration having a first leg 62 contactable by the arm 59 of the frame 57 and a second leg 64. At the intersection of the first and second leg 62, 64, the latch 49 has an opening 66 corresponding to the shape of a quadrant of approximately 270°. The opening 66 is cooperable with a quadrant shaped projection 68 which is complementary to the quadrant shaped opening 66, except that the projection 68 is of a lesser angle thereby enabling the latch 49 to pivot a few degrees about the projection 68. The shape of the opening 66 and the projection 68 thus define a pivot range for the latch 49 about a main axis 67. A compression spring 70 best seen in Figure 3 biases the second leg 64 toward the left of the Figure. One end of the compression spring is captive in a recess (not shown) in the interior of the housing while the other end of the compression spring 70 is wound around a boss (not shown) formed as part of the second leg 64. The lower end of the second leg 64 also defines a ledge 72 cooperable with one end of the contact carrier 35 in a manner which will be explained subsequently. Figure 4a illustrates the contact carrier 35 in engaged configuration on the ledge 72. It will be appreciated when the arm 59 of frame 57 moves upwards, the latch 49 will be caused to rotate about the main pivot 67 against the bias of spring 70 to release the contact carrier 35 from engagement with ledge 72.

The latch 49 has its two legs 62, 64 extending in generally the same plane which is substantially aligned with the main plane of the housing.

Contact Carrier 35

As already described in connection with Figure 1, the contact carrier 35 carries two moveable contacts 32. The moveable contacts 32 are connected to leads 39. The moveable contacts 32 engage with respective ones of the fixed contacts 30.

Reference is made to Figures 1 and 6. The moveable contact carrier 35 is a moulded plastic construction having a pair of spaced lobes 74 with aligned apertures therein through which a mounting pin 75 extends. The ends of the pin 75 are received in respective bosses 87 formed in the sides of the contact carrier 35. The bosses are received in aligned vertical slots formed in the interior of the housing on opposite sides. Furthermore, the contact carrier 35 includes a central lug 77. A spring 79 has one end connected to a projection in the housing and the other end connected to the lug 77. The spring 79 biases the right hand end of the contact carrier (from the perspective illustrated in Figure 1) upwardly.

The contact carrier 35 also incorporate an extension 114 as shown in Figure 6 engageable with the ledge 72 of the latch 49.

Further, the contact carrier 35 incorporates a downwardly projecting web 81 (see Figure 1), generally aligned with the main plane of the housing and disposed approximately centrally relative to the thickness of the housing 12. As can be appreciated most clearly in connection with Figure A, the web 81 is arranged to extend between each of the two contact sets 30, 32 to prevent arcing therebetween when the contacts are closing or opening.

Additionally, from Figure 4 an auxiliary contact in the form of a spring arm 83 is shown. One end of the spring arm 83 is fixed. A fixed auxiliary contact 85 is provided at a proximate edge of the circuit board 45. When the contact sets 32, 30 are closed as shown in Figure 4, the web 81 pushes down on the spring bar 83 to cause the other end of the spring bar 83 to make contact with the fixed auxiliary contact 85. As will be explained in connection with Figure 14, the auxiliary contact set is provided to break the power to the solenoid 47 in the event that the device 10 is wired with load and line reversed from their intended configuration. When the main contact set 30, 32 is broken the web 81 will move upward with the contact carrier 35 thereby enabling the spring bar 83 to spring back into spaced configuration from the fixed auxiliary contact 85. The power to the solenoid 47 will be broken, even if the RCD is wired back to front. Otherwise, power to the solenoid of a duration even exceeding a second will cause the solenoid 47 to burn out. This will be explained further in connection with Figure 14.

Contact Carrier 35 and Reset Mechanism

Figure 6 and 7 show the contact carrier 35 and part of the reset mechanism in greater detail. As already explained, mounting pin 75 extends between side lobes 74. Part of the foremost lobe shown in Figures 6 and 7 has been removed for the purposes of clarity. As already explained, the ends of the mounting pin 75 are journaled in the side lobes 74 of the contact carrier. The side lobe 74 form raised bosses 87 around the ends of the mounting pin 75. These enlarged bosses 87 are received in aligned vertical slots 88 formed on the inner opposing faces of the side walls of the housing 12 as shown in Figure 5a. The bosses 87 engaging in the corresponding slots enable the contact carrier to move up and down as required when moving between the latched position and the unlatched position (see Figure 5a).

Reverting to Figure 1 the actuator 51 is pivotally mounted so as to protrude through the front region 14 of the housing. The actuator 51 has a circular body portion 90 pivotally mounted to be selectively rotatable about a transverse pivot axis. A handle portion 92 extends radially from the body portion 90 for actuation by the user. As shown in Figures 1, 6 and 7, a link member 94 is pivotally mounted to the body portion 90 by means of a pin 96. Referring to Figure 6, the link member 94 is not shown in full but has a forward portion removed for clarity. The link member 94 is symmetrical about the cut. The link member 94 has two side walls 100, the top ends of which carry the pin 96 and two end walls 102. The two end walls 102 together with the side walls 100 define a central cavity housing a separate connecting member 104. The connecting member 104 includes a loop portion 106 extending about mounting pin 75 and a carrier portion 108 which provides a seat for a strong spring 110. The spring 110 is wound around a central dependency 112 from the link member 94. The spring 110 biases apart the connecting member 104 and the link member 94 towards the configuration illustrated in Figure 6 where cooperating shoulders of the link member 94 and the connection portion 108 engage to thereby define their limit of movement away from each other.

Figure 6 illustrates the position of the link member 94 when the actuator is disposed in the unlatched position illustrated in Figure 2. In the unlatched configuration illustrated in Figure 2, the actuator 51 is held in the position shown by an incorporated torsion spring (not shown). Additionally, spring 79 biases the contact carrier 35 upwardly so that the bosses 87 are located at the uppermost extent of the slots within which they are received. When it is desired to close the contacts, the actuator 51 is rotated about its pivot axis towards the position illustrated in Figure 4. As the actuator 51 is rotated, the pin 96 which is pivotally connected to the periphery of the body of the actuator 51 will be moved in a circular path, down and towards the left from the viewpoint of Figure 2. The spring 110 is a very strong spring exceeding the force of spring 79 biasing the contact carrier 35 in the upward position. The spring 110 transmits the downward movement to the connecting member 114 which in turn pushes down on the mounting pin 75 which accordingly moves the bosses 87 downwardly within the corresponding slots on the inside of the housing. The slots constrain the movement of the bosses 87 to up and down movement. Hence the pin 96 will be caused to rotate about pin 75 as it moves in its arcuate path about the pivot axis of the actuator 51. As the contact carrier 35 is pushed downwardly, the extension 114 will initially contact the ledge 72 of the latch 49. Thereafter, as the contact carrier continues to be pushed downwardly, the contact carrier will rotate about ledge 72 until the contact sets 30, 32 close.

After the contact set 30, 32 close, if the pin 96 is to continue in its arcuate path, the link member 94 must slide relative to the connecting member 104, against the bias of spring 110. At the lowest point in the arcuate path of pin 96, the spring 110 will be in its most compressed state. This corresponds to a lining up of the pivot axes of the actuator 51, the pin 96 and the pin 75. The spring relaxes slightly as the pin 96 is moved to an over- centre position shown in Figure 7, corresponding to Figure 4. In the over-centre position of Figure 4, the actuator 51 has reached the extent of its travel and the action of spring 110 against link member 94 now only serves to maintain the actuator 51 in the latched position with the contact sets 30, 32 closed.

RCD Trip Out

The RCD illustrated is of the type in which the solenoid 47 is normally in a de-energised state when the contact sets 30, 32 are closed and is only briefly energised to break the contacts when a fault condition is detected. The sensor coil 42 as described has active and neutral leads 39 passing centrally through a core over which is wound a secondary winding of high inductance. The conductors are effectively anti-phased primary windings such that normal load currents cancel each other resulting in zero output from the secondary winding. An output voltage is developed when a small residual current from the load active flows back to line neutral indirectly, usually via ground, from a faulty appliance or cable connected to the load. The fault detection circuitry illustrated in Figure 14 and explained in greater detail below sends current to the solenoid 47 when a fault is detected. Energisation of the solenoid 47 results in the plunger being pulled inwardly into the body of the solenoid with the connected frame 57 and associated contact arm 59 being moved upwardly. The contact arm 59 in its upward path engages the first arm 62 of the latch 49 to rotate the latch 49 about the main pivot 67 to thereby release the projecting end 114 of the contact carrier from the ledge 72. With the contact carrier 35 released from the ledge 72, the corresponding end of the contact carrier 35 drops. This allows the link member 94 to slide relative to the connecting member 104 under the bias of spring 110 until the cooperating shoulders reengage to define the extent of their travel. Once the effect of spring force 110 which was acting to bias the actuator into the over-centre position is reduced, the actuator 51 will be operated upon by its incorporated torsion spring causing a traversal of the actuator 51 back to the unlatched position with a consequent arcuate movement of the pin 96 which in combination with the action of spring 79 both tend to pull the right end of the contact carrier 35 out of engagement with the fixed contacts 30. The spring 79 also assists if the actuator 51 is held by the user in the latched position as shown in Figure 5. From Figure 5, it can be seen that the spring 79 still acts to bias the contact carrier 35 upwardly as shown. However, normally, the unlatched position would be that of Figure 2. The spring 79 also acts to prevent closing of the contacts in the event that the contact carrier is not properly engaged with ledge 72 on latch 49 (see Figure 5).

Indicator Flag

Figure 1 illustrates an indicator flag 120 which is pivotally mounted in the housing. The indicator flag 120 has an arcuate indicator surface having at least two indicia portions which can be viewed through a window in the front portion 14 of the housing. The position of the arcuate portion determines which of the indicia portions are viewable through the window. The position of the arcuate portion is changed by rotating the indicator flag and its pivotal position is determined by engagement between the remote end of the indicator flag 120 and the contact carrier 35.

Vents

Figure 1 also illustrates arc chute which comprises a series of vents 130 in communication with an aperture 132 in the housing to permit escape of any smoke or fumes caused by arcing of the contacts.

Detailed Description of Fault Detection Circuit

Figure 9 shows a control circuit 300 which could be used with the RCD of Figures 1 to 5. This is based on a Raytheon RV4145 ground fault interrupter integrated circuit IC1. A sensor coil in the form of differential toroidal transformer 42 has mains active and neutral conductors 39a and 39b passing centrally through a core over which is wound a secondary winding 302 of high inductance. The conductors are effectively anti-phased primary windings such that normal load currents cancel each other resulting in zero output voltage from the secondary winding. An output voltage is developed when a small residual current from the load active flows back to line neutral indirectly, usually via ground, from a faulty appliance or cable connected in the load. A metal oxide varistor VDR1 is provided to limit peak mains transients from causing damage to the circuit or any attached appliance. Power is supplied to the circuit by a half wave rectifier Dl and current limiting resistors R2A, R2B to Capacitor C2 which in turn supplies power to the control circuit. The solenoid LI is in series with this circuit, so as long as pin SCR is not energised, no significant current flows through the solenoid.

One end of coil 42 is connected to IC 1 at pin 3 which is a common amplifier reference point. Capacitor C5 filters high frequency noise from the secondary voltage, while capacitor C4 provides noise bypassing from the bulk of the coil to IC 1 at ground pin 4. The active end of coil 302 is connected to an amplifier summing junction at pin 1 through capacitor C6 and resistor R4. Resistors R4 and R3 determine the amplifier gain while capacitor C6 series resonates with the coil inductance and is designed to extract mains frequency signal components from loads which use half wave power control. Otherwise the core would saturate from the resulting DC and produce very little output to trip the switch. Capacitor C7 provides amplifier high frequency roll off.

The amplifier output is internally connected to comparators which are referenced to zener diodes in IC 1. When the amplified signal detected on pin 1 exceeds the zener thresholds, an output signal at pin 5, filtered by a capacitor C3, triggers a silicon controlled rectifier TRl. The SCR TRl latches and shorts the supply across Cl, so that the full mains voltage appears across solenoid LI. This activates plunger 7 to cause opening of the contacts as described, turning off power to the load as well as the control circuit of this device. The control circuit is thus de-energised and the solenoid is deactivated. At this point the RCD may be reset by rotating actuator 51 as previously described to close the contact sets 30, 32 enabling the closing of the contacts as described.

A circuit test means is provided by which unbalanced current is passed through the transformer core to check action of the switch. Button 305 (see also Figure 1) is pressed to complete a link between the active an neutral conductors, taking a portion of the active current determined by resistor 39 through the transformer twice. This simulates a residual current flowing from the neutral conductor and escaping to earth. Auxiliary Contact

As described, the auxiliary contact 83, 85 is operated by the action of web 81 so that when the contact set 30, 32 are closed, the auxiliary contact set 83, 85 is closed. When the auxiliary contact sets 83, 85 is closed this completes the circuit between the active load and the neutral load through the solenoid and control circuit and allows the unit to function as described above. As also described above, after the device trips under a fault condition, the solenoid and the control circuit are then de-energised (and the device can also be tripped manually). However, if the connection of the device is incorrect in that the line or supply is connected to the load terminals the voltage would remain present unless the auxiliary contact set opened. If the auxiliary contact set did not open, the control circuit would not reset and the mains voltage across the solenoid and control circuit would, in short time, damage components not designed to withstand mains voltage for extended periods. The action of the auxiliary contact set in breaking the circuit between the active load and the neutral load removes the voltage even when the supply is wired to the load side of the main contacts 30, 32.

Claims

CLAIMS:

1. A circuit interruption device for mounting to a distribution rail or on a distribution board including:

a housing having length, depth and thickness with the thickness dimension being the smallest, and the length and depth defining a main plane of the housing; a circuit board of planar configuration mounted within the housing so that the plane of the circuit board is substantially aligned with the main plane of the housing, the circuit board providing a mounting for at least some components of a fault detection circuit to detect a fault condition; a trip device, a latch and a contact set, which trip device will in response to detection of a fault condition trigger the latch to open the contact set, the latch having length, breadth and thickness and being disposed within the housing with its length substantially aligned with the main plane of the housing, and one of the contact set being supported by a moveable contact carrier having length and being disposed within the housing with its length substantially aligned with the main plane of the housing; and, a reset mechanism to reset the contact carrier to close the contact pair, the mechanism including an actuator having length and which is arranged in relation to the housing with it's length substantially aligned with the main plane of the housing.

2. A circuit interruption device according to claim 1 comprising two contact sets and wherein the movable contact carrier supports a contact of each contact set.

3. A circuit interruption device according to either of claim 1 or claim 2 wherein the housing includes end portions at each end for terminal connections in which are mounted terminals substantially aligned with the main plane of the housing.

4. A circuit interruption device according to any one of claims 1 to 3 wherein the housing includes a central portion defining a main internal housing cavity housing the circuit board, trip device, latch, contact set(s) and contact carrier, and the reset mechanism and wherein the actuator, part of the reset mechanism protrudes through a front wall of the central portion of the housing.

5. A circuit interruption device according to any one of claims 1 to 4 including a fault detection circuit including a sensor coil, through which active and neutral conductors pass and wherein the axis of the coil is maintained within the housing to lie substantially aligned with the main plane of the housing enabling the conductors to pass through the sensor coil generally aligned with the main plane of the housing.

6. A circuit interruption device according to claim 5 wherein the sensor coil straddles the circuit board and the two conductors pass on either side of the circuit board.

7. A circuit interruption device according to any one of claims 1 to 6 wherein the circuit board is generally centrally disposed relative to the thickness of the housing.

8. A circuit interruption device according to any one of claims 1 to 7 wherein the trip device is a solenoid with an elongate body including a solenoid coil and a moveable plunger operable to trigger the latch, and wherein the solenoid is mounted within the housing so that the length of the body is arranged to be aligned within the main plane of the housing.

9. A circuit interruption device according to claim 8 wherein the solenoid coil is wound such that its resultant transverse shape has a first transverse dimension less than a second transverse dimension orthogonal to the first transverse dimension.

10. A circuit interruption device according to claim 9 wherein the solenoid coil is wound over a bobbin having a rectangular or oval cross-sectional shape.

11. A circuit interruption device according to any one of claims 8 to 10 wherein the thickness dimension of the coil is mounted within the housing so that the transverse dimensions of the coil are aligned with the thickness dimension of the housing.

12. A circuit interruption device according to any one of claims 1 to 11 wherein the latch is L-shaped having one arm which is engaged by the trip device on tripping and another arm which engages the contact carrier to hold the contact carrier in a position when the contact set is closed.

13. A circuit interruption device according to claim 12 wherein the thickness of the latch is aligned with the thickness dimension of the housing.

14. A circuit interruption device according to claim 13 wherein the latch pivots about a main pivot, the axis of which is aligned with the thickness dimension of the housing.

15. A circuit interruption device according to any one of the preceding claims wherein the latch and the trip device are disposed on opposite sides of the circuit board.

16. A circuit interruption device according to any one of claims 1 to 15 wherein there are two terminal connectors at each end of the housing.

17. A circuit interruption device according to any one of the preceding claims comprising two contact sets each of which comprises a moveable contact and a fixed contact, the movable contacts being mounted on a moveable contact carrier and the fixed contacts being mounted side by side, wherein the moveable contact carrier incorporates a barrier portion disposed to extend between the two fixed contacts when the position of the contact carrier is such that the contact sets are closed.

18. A circuit interruption device according to claim 17 wherein the barrier portion is integrally formed as part of the contact carrier.

19. A circuit interruption device according to claim 18 wherein the barrier portion is operable to effect engagement between an auxiliary contact set.

20. A circuit interruption device according to claim 19 wherein the auxiliary contact set is provided such that in the event of the circuit interrupter being wired incorrectly, the movement of the moveable contact carrier to break the primary contact sets will effect breaking of the auxiliary contact set.

21. A circuit interruption device according to claim 20 wherein the moveable contact is a spring bar and the fixed contact is defined on an edge of the circuit board.

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